1. Field of the Invention
The invention relates to a thrust reverser device for a bypass turbojet.
More particularly the invention relates to a turbojet thrust reverser comprising, in an annular section of an outer cowling surrounding a gas ejection duct, a fixed structure comprising longitudinal spars delimiting passages between them, and a plurality of movable doors which, in an inactive position during operation of the turbojet in forward thrust, close off said passages and constitute part of the outer cowling and which, in a reverse thrust configuration, at least partially close off the ejection duct and deflect a gaseous jet toward the passages.
The doors are moved by control means consisting, for example, of rams supported by a rigid front frame situated upstream of the passages. The doors are generally mounted, in an intermediate region of their side walls, by pivots to the spars. In the reverse thrust configuration, the doors pivot in such a way that a part of the doors situated downstream of the pivots more or less completely closes off the bypass or cold stream and in such a way that an upstream part of the doors uncovers the passages in the outer cowling so as to allow the bypass stream to be routed radially with respect to the axis of the turbojet.
The upstream part of the doors projects out from the outer cowling for reasons of sizing of the passage which has to be capable of allowing this stream to pass through without compromising engine operation. The angle of pivoting of the doors is adjusted so as to allow the stream to pass and in such a way as to destroy the thrust of this stream, or even to begin to generate backthrust by creating a component of the stream deflected in the upstream direction.
The role of the thrust reverser in reverse thrust mode is to create reverse thrust which slows down the aircraft particularly when it is running along a runway after landing.
It is therefore essential that the doors be kept in the inactive or closed position during flight. This is why systems are provided for locking the doors in the closed position.
2. Summary of the Prior Art
In the event of an engine disk shattering, the reverser may sustain serious damage. In the (albeit unlikely) event of this happening, the reverser must not, in spite of this, deploy to the reverse thrust configuration. To achieve this objective, it is possible to use lateral locks usually fitted into the fixed structure of the reverser and situated at a longitudinal position remote from another door-locking system so that the debris of a disk cannot simultaneously hit both reverser door locking systems.
Reverser safety with regard to inadvertent deployment may be enhanced generally, and not just for the eventuality of the shattering of an engine disk, by adding a third lock which may lessen the effect of failure of the other locking systems if necessary. This addition enhances the reliability of the locking systems. Now, in the current state of the art, this lock is equipped with a control system more or less independent of that of the other locking systems. This lock generates an increase in mass and, to a certain extent, a reduction in the reliability of the control system.
The philosophy behind improving the resistance to shattered engines consists in securing as many moving parts of the reverser as possible. It is therefore highly advantageous to synchronize the opening of two doors of a door-type thrust reverser, because the probability of damaging the members that retain each of two doors in the event of a breakage is far lower than the possibility of breaking the locking system for just one door.
One possible solution consists in synchronizing the moving parts of the reverser, to give a mechanical line of defense independent of the reverser control system. However, the devices for synchronizing the doors are generally heavy. These are often ram synchronizing screws, whose reliability as locking members is sometimes debatable.
Finally, it is extremely tricky to synchronize the doors via their pivots, because of the significant torques generated by the pressure forces to which they are subjected.
The object of the invention is to provide a thrust reverser as defined in the introduction and in which the doors are held in the closed position if an engine shatters or if there is complete failure of the locking system of one door.
Another object of the invention is to provide a thrust reverser which comprises a passive locking system, the operation of which is based on synchronizing the opening of two doors of the thrust reverser, without any external control member.
Accordingly the invention provides a thrust reverser for a turbojet having an outer cowling surrounding a gas ejection duct, said thrust reverser comprising a fixed structure including longitudinal spars delimiting passages between said spars in an annular section of said cowling, and a plurality of doors mounted to move between an inactive position occupied during forward thrust operation of said turbojet wherein said doors close off said passages and constitute part of said outer cowling, and a reverse thrust position wherein said doors at least partially close off said ejection duct and deflect the gaseous jet toward said passages, wherein there is provided, between two adjacent doors of said thrust reverser, a locking system allowing substantially simultaneous opening of said two doors, said locking system comprising, for each of said two doors, at least one hook mounted on said fixed structure so that it can pivot between a door locking position and an unlocked position, at least one olive secured to each of said two doors for engaging and pivoting said hooks during opening or closing movement of said doors, and a mechanical linkage device rotationally interconnecting the hooks of said two doors so as to prevent the unlocking of one door if the other door is closed.
The following advantageous provisions are also adopted:
each hook comprises an olive housing delimited by a lower internal profile and an upper internal profile, said internal profile being configured in such a way that said lower internal profile is constantly in the path of the corresponding olive and said upper internal profile can move out of said path, and in such a way that said olive exerts a locking torque when it presses against said lower internal profile and exerts an unlocking torque when it presses against said upper internal profile;
each hook is urged toward said unlocked position by resilient means;
said unlocked position of said hook is defined by a stop; and
said olive is mounted on a retractable support so as to allow non-simultaneous closure of said two doors, this support being urged toward an active position of said olive by resilient means.
According to a first embodiment of the invention, said hooks are mounted so that they can pivot about pivot pins substantially parallel to the axis of rotation of the turbojet.
The mechanical linkage device may consist of two intermeshed toothed sectors, formed respectively in peripheral walls of said hooks and centered on said pivot pins.
The mechanical linkage device may comprise a link rod articulated at each end to a respective one of said hooks by means of a ball-type joint.
As a preference, the mechanical linkage device comprises at least two link rods, each link rod being articulated in the manner of a ball joint to a respective hook by one of its ends and being connected slidingly to the other hook by the other end so that said link rods work mainly in tension.
According to a second embodiment of the invention, each hook is mounted so that it can pivot about the axis of a transmission shaft substantially parallel to the pivot pin of the corresponding door. The mechanical linkage device transmits torque between said two transmission shafts, and is, for example, of the cardan type.
According to an alternative form of this second embodiment, each hook is mounted so that it can pivot about a transmission shaft parallel to the pivot pin of the corresponding door, which shaft is rotationally linked to a transmission shaft of a control latch associated with the other door, said control latch being capable of being driven in rotation between a locked position and an unlocked position by a second olive with which the other door is equipped. Each hook comprises an upper internal profile preventing said hook from rotating when said olive is pressing against said profile as a consequence of premature opening of said door.